Biosynthesis and metabolism of purine alkaloids in leaves of cocoa tea (Camellia ptilophylla)

The biosynthesis and metabolism of purine alkaloids in leaves of Camellia ptilophylla (cocoa tea), a new tea resource in China, have been investigated, The major purine alkaloid was theobromine, with theophylline also being present as a minor component. Caffeine was not accumulated in detectable quantities. Theobromine was synthesized from [8-C-14]adenine and the rate of its biosynthesis in the segments from young and mature leaves from flush shoots was approximately 10 times higher than that from aged leaves from 1 year old shoots. Neither cell-free extracts nor segments from C. ptilophylla leaves could convert theobromine to caffeine. A large quantity of [2-C-14] xanthine taken up by the leaf segments was degraded to (CO2)-C-14 via the conventional purine catabolic pathway that includes allantoin as an intermediate. However, small amounts of [2-C-14] xanthine were also converted to theobromine. Considerable amounts of [8-C-14] caffeine exogenously supplied to the leaf segments of C. ptilophylla was changed to theobromine. These results indicate that leaves of C. ptilophylla exhibit unusual purine alkaloid metabolism as i) they have the capacity to synthesize theobromine from adenine nucleotides, but they lack adequate methytransferase activity to convert of theobromine to caffeine in detectable quantities, ii) the leaves have a capacity to convert xanthine to theobromine, probably via 3-methylxanthine.